1. Field of the Invention
This invention relates to a plate feeding apparatus for transporting stacked printing plates in order from an uppermost plate, and in an inverted state, to a processing unit at a subsequent stage.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2000-247489, for example, discloses a plate feeding apparatus for transporting printing plates, in an inverted state, to a nip roller. According to this apparatus, a suction point at a leading end of each plate sucked and held by suction pads is moved to coincide with a cycloid formed when a circle having a radius equal to the turning radius of the suction point rolls over the plate surface. Subsequently, the leading end of the plate is pinched by the nip roller.
Such a plate feeding apparatus that transports printing plates, in an inverted state, to the nip roller has an advantage of transporting the plates reliably without occupying a large space even when transporting relatively large plates.
In such a plate feeding apparatus, plates are usually stacked with end edges made even by a stopper. Then, with the plate feeding apparatus that transports the plates, in an inverted state, to the nip roller, when a distance from a plate storage unit to the nip roller is small for the size of the plates, the rear end of a plate will thrust itself in between the end edges of the plates stacked and the stopper, making it impossible to transport the plate properly.
This inconvenience will be described with reference to FIGS. 21A and 21B. FIGS. 21A and 21B are schematic views showing an operation to transport printing plates P.
No problem arises in transport of printing plates P when, as shown in FIG. 21A, an uppermost plate P is raised at a predetermined angle α1 to the rest of the plates P stacked. On the other hand, when the angle α1 becomes small as shown in FIG. 21B, the end of the plate P adjacent a stopper 201 will take a vertical position. There occurs a phenomenon of the end of the plate P adjacent the stopper 201 thrusting itself in between the end edges of the stacked plates P and the stopper 201. Such a phenomenon causes a problem that the plate P cannot be transported properly.
In order to solve this problem, it is conceivable to secure a sufficiently large distance from the plate storage unit to the nip roller in accordance with the size of the plates. However, the increasingly large printing plates used nowadays will result in the entire apparatus occupying a large space.